A workaround is to copy secdrv.sys from a windows 8 / 8.1 machine, self sign the driver, and enter into testsigning boot mode.

You can do this manually or use 3rd party programs to do it.

First copy secdrv.sys from a windows 8 machine to c:\windows\system32\drivers. You can also download it here. Same file as the one I got from a vanilla windows 8.1 install v 4.3.86.0 md5 3ea8a16169c26afbeb544e0e48421186